This invention relates to tension or strand-length compensation in strand winding operations, and particularly the winding of a strand on a conical core to form a strand package. More particularly, the invention relates to such compensators which may be automatically loaded.
When packages are formed by winding a strand in a helix on a package core, the length of the strand between the supply and the package is not constant since the distance from the supply to the ends of the package are greater than the distance to the intermediate locations. This resuls in uneven tension in the strand on the package which may produce undesirable changes in the physical properties of the strand as well as unsatisfactory formation of the strand package itself. This condition is exaggerated in cone winding because the peripheral speed of the conical package core varies continuously from one end to the other even through the angular velocity is constant. This condition exists to varying degrees whether the strand is fed to the winding station at either variable or fixed rates. However, the problems are particularly evident when the strand is fed at a fixed rate to the winding station, as, for example, in the winding of yarn produced by open end spinning wherein the yarn is fed to the winding station at a fixed rate determined by the feed of the yarn withdrawal rolls.
In order to remedy this problem, tension compensators have been employed to store strand when the tension is low and to release strand from storage when the tension is high. Many such compensators have two spaced pins or projections mounted on a member rotatable about a fixed axis, the pins extending generally in the direction of, substantially parallel to and on opposite sides of the axis. The member is biased to rotate in a predetermined direction and the strand between the supply and the package is threaded over one pin and under the other in a zig-zag manner such that tension in the strand exerts force on the pins tending to rotate the member in opposition to its bias. The bias typically may be adjusted so that it overcomes the force of the strand on the pins when tension is low, thereby storing strand, and the bias is overcome by the force of the strand on the pins when tension is high, thereby releasing strand from storage. Thus, in winding conical packages, the compensator will store strand when the strand is traversed toward a small end of the cone and will release strand when the strand is traversed toward the large end of the cone.
Since manual loading or threading of the strand through the tension compensator is considerably time consuming, it is desirable to provide a means for self-loading or automatic loading of the tension compensator. One such self-loading tension compensator is disclosed in Richard A. Schewe's U.S. Pat. No. 4,133,493.
In order to accommodate variations in the strength of different strands encountered in winding different types of yarn and to accommodate cones of different sizes which may be used in package winding, it is desirable to employ a compensator having a greater range of strand storing capabilities beyond that which can be obtained simply by adjusting the bias on the rotatable member. Such increased range can be achieved by designing the compensators so that the rotatable member and its associated pins can oscillate through a larger angle. It has been found that the self-threading feature disclosed in Schewe's U.S. Pat. No. 4,133,493 is not completely satisfactory when the range of rotation of the rotatable member is substantially increased. Consequently, there has been a need for a tension compensator having a greater range of compensation which can be reliably automatically loaded or threaded-up.